Electrical induction furnace



Dec. 26, 1933. L. DREYFUS 1,941,075

ELECTRICAL INDUCTION FURNACE Filed Jan. 5, 1933 N [LIA Patented Dec. 26, 1933 PATENT OFFICE ELECTRICAL INDUCTION FURNACE Ludwig Dreyfus, Vasteras, Sweden, assignor to Allminna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Application January 5, 1933, Serial No. 650,279, and in Sweden January 2, 1932 2 Claims.

In electric induction furnaces not having a closed iron circuit, but having a cylindrical primary coil, it is customary to surround the said coil with an iron shell consisting of sheet iron bundles having the plates arranged in planes substantially through the axis of the furnace. The lines of force produced by the winding will as is evident from reasons of symmetry practically all he in such planes. The shell composed in this way must, however, generally have interruptions or intervals in different places, for instance for theconnections to the winding, in the first line at the ends thereof but frequently also in other points or for the connection to cooling conduits. Such intervals in the shell may also arise from the fact that the laminations, which generally consist of plates of uniform thickness, are generally combined to bundles for practical constructional reasons, each of the said bundles generally embracing only a small portion of the periphery of the furnace. At such intervals the lines of force will in part run perpendicular to the surface of the plates which at the high frequency generally employed will cause large local losses and consequent strong heating.

For protecting the sheet iron bundles against such lines of force penetrating perpendicularly into the plate surface, there are arranged according to the present invention at the side of the sheet iron bundles at the places of interruption other bundles of iron wire the longitudinal direction of the wire substantially coinciding with that of the plates. Each of the wires is insulated in a suitable manner, for instance by enamel. The section of such bundles may be substantially semi-circular, and the wire diameter should be of the same order of magnitude as the plate thickness, for instance 0.5 millimetre. It is of importance that such wire bundles should be introduced in the large intervals in the iron shell, for instance at connecting rails or cooling pipe connections; they may, however, also be placed in the small intervals.

One form of the invention is diagrammatically shown in a front view in Fig. 1 and in a horizontal section in Fig. 2 of the accompanying drawing.

1 is a furnace crucible, 2 an insulating layer, 3 the furnace winding and 4 the sheet iron bundles of the shell. In the form shown, the latter are secured in pairs in holders 5, which in their turn are supported by a common frame 6.

In one place of the circumference there is a comparatively broad opening between the sheet iron bundles for introducing the connecting rails '7 to the winding 3 and possibly for other elements as connecting pipes for cooling serpentines. At both edges of this broad opening the sheet iron bundles are screened by bundles 8 of insulated iron wire,

to run perpendicularly to its surface and thereby 8 to cause large eddy-current losses.

I claim as my invention:--

1. In electrical induction furnaces, a furnace receptacle, a substantially cylindrical induction coil surrounding same, longitudinal sheet iron bundles grouped around said coil on the major portion of its periphery, and iron wire bundles placed along the sides of certain of said sheet iron bundles.

2; In electrical induction furnaces, a furnace receptacle, a substantially cylindrical induction coil surrounding same, terminal conductors proiecting substantially radially outwards from said coil, longitudinal sheet iron bundles grouped around said coil, and iron wire bundles placed along the sides of said sheet iron bundles facing said terminal conductors.

LUDWIG nam'os. 

